| As one of the most effective ways to reduce friction and wear between moving parts,lubricating oil has been widely used.However,although traditional lubricating oil has excellent lubrication performance,it is very easy to be "extruded" when used under heavy load conditions,resulting in direct contact of friction pairs,Therefore,we need to find a new type of nano additive to meet the traditional lubricating oil failure under heavy load conditions,still can play a lubricating effect on the friction pair.Graphene has become the star material of today’s research,with its excellent optical,thermal,electrical,mechanical properties and other characteristics.However,when graphene nano powder is used as lubricating oil additive,there are many problems,such as easy agglomeration,uncontrollable uniform dispersion and so on,which restrict the development and application of graphene modified lubricating oil.In order to solve the above problems,a new method of graphene surface modification was proposed in this paper.Graphene composites loaded with ceria(CeO2)nano particles were prepared by one-step hydrothermal method.From the perspective of tribology,the antifriction performance of graphene as pao5w-40 lubricating oil additive was studied,and its antifriction mechanism was analyzed.The main research results are as follows:1.CeO2 nanoparticles with the grain size of 6.64-11.84 nm were grown in rGO nanosheets by a new process of blending-hydrothermal-freeze-drying,the reduced graphene oxide powder loaded with CeO2 nanoparticles was obtained(CeO2/rGO).2.The activation index of CeO2/rGO nano powders,Zeta potential values of CeO2/rGO nano powders in PAO5w-40 lubricating oil and the layered precipitation phenomenon of CeO2/rGO-1:3,CeO2/rGO-1:1,CeO2/rGO-3:1 nano powders as lubricating additive in lubricating oil were analyzed:Activation indexs(the activation indexs of CeO2/rGO-1:3,CeO2/rGO-1:1,CeO2/rGO-3:1 were 36.8%,41.6%and 64.1%respectively);Zeta potential values(the zeta potential values of CeO2/rGO-1:3,CeO2/rGO-1:1 and CeO2/rGO-3:1were-27.578,-28.099,-33.805,-33.827mV);Macroscopic phenomenon of liquid level stratification(the nano powders of rGO,CeO2,CeO2/rGO-1:3,CeO2/rGO-1:1 had obvious delamination and precipitation after standing in lubricating oil for one month,while the nano powders of CeO2/rGO-3:1 had no obvious precipitation and stratification after standing in the lubricating oil for one month).3.The effect of nano powder on the viscosity and corrosion of lubricating oil at a specific temperature was studied:the viscosity of base lubricating oil was increased by rGO、CeO2、Ce2/rGO-1:3、CeO2/rGO-1:1 nano powders,while added CeO2/rGO-3:1 nano powder reduced the viscosity of-base lubricating oil and improve the fluidity of lubricating oil;Compared with the copper corrosion card,adding several kinds of graphene nano powder didn’t increase the corrosivity of lubricating oil.4.The friction performance of lubricating oil containing nano powder additives was tested by POD ball-disc friction and wear tester.When the mass ratio of nano powder additive was 3%,adding CeO2/rGO-3:1 nano powders lubricating oil had the best performance,and compared with pure PAO5w-40 lubricating oil,the friction coefficient,wear scar depth and wear volume of adding CeO2/rGO-3:1 nano powders lubricating oil were reduced by 31.9%,23.1%and 83.3%,respectively. |
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